Snap action electric switch



United States Patent ABSTRACT: A snap action electric switch includes a housing having a pair of stops in spaced relation and forming first and second electrical contacts, and a switch actuating member displaceably mounted in the housing. A third electrical contact forms a fulcrum for an intermediate portion of a two arm electrically conductive angle lever which is engaged by the actuating member. An electrically conductive contact arm has one end bearing pivotally on one arm of the lever and its other free end movable between the first and second contacts. A tension spring has one end connected to a first suspension point on the contact arm and its opposite end connected to a second and fixed suspension point on the housing beyond the fulcrum and beyond the other arm of the lever. The line of action of the tension spring always remains in spaced lateral relation to the same side of the fulcrum in all positions of the switch. A pair of abutments on the other arm of the lever embrace the tension spring between the lever fulcrum and the fixed suspension point and deflect the tension spring to one side of the straight line interconnecting the first and second suspension points.

The tension spring, acting through the contact arm, exerts a torque tending to pivot the lever in one direction about the fulcrum, and the deflection of the tension spring by the abutments exerts a torque tending to pivot the lever in the opposite direction about the fulcrum. The two torques, acting in opposite directions, result in only a small force on the actuating member being necessary to snap the contact arm from a rest position to an actuated position. In the actuated position, the abutments deflect the tension spring in the opposite direction relative to the straight line connecting the first and second suspension points, so that the spring exerts a restoring force on the contact arm. Preferably the contact arm and the lever arm upon which it bears are forked to provide for passage of the tension spring between the arms of the forks.

[72] Inventor Ewald Marquardt Rietheim, Germany [2]] Appl. No. 677,114 [22] Filed 0ct.23, 1967 [45] Patented Dec.15,1970 [73] Assignee Firma J. &J.Marquardt Rietheim, Kries Tuttlingen, Germany [32] Priority 0ct.26, 1966 [33] Germany [31 No. 1,665,082

[54] SNAP ACTION ELECTRIC SWITCH 5 Claims, 2 Drawing Figs.

[52] 1.1.8. Cl 200/67 [51] lnt.Cl. ..H0lh 13/28 [50] Field ofSearch 200/67, 67(B),67(D) [5 6] References Cited UNITED STATES PATENTS 3,233,057 2/1966 Aschwanden 200/67B(UX) 3,327,946 6/1967 Benson 200/67B(UX) FOREIGN PATENTS 566,762 1/1945 GreatBritain 200/67D(UX) 1,235,404 3/1967 Germany 200/67B(UX) Primary Examiner-Robert S. Macon Assistant Examiner-D. Smith, Jr. Attorney-McGlew and Toren PATENTEU 0501 5 I970 BY MWM ATTORNEY!) BACKGROUND OF THE lNVENTlON The present invention is directed to that type of snap action electric switch including a contact arm pivotally displaceable between two stops and which is biased, by an-extension spring, into bearing engagement on a means adjustable as a function of the switch-actuating member, this means being mountedat a point outside of any possible direction of action of the spring and being returned to its rest position by the extension spring, after adjustment thereof as a function of the switch-actuating member. f'

ln snap action switches of this type, the fixed contact engaged by the contact arm in theactuated position-of the latter and the rest contact engaged by the contact arm in its rest position are frequently spaced quite considerably from each other. It is desirable to reduce the distance through which. the free end of the contact arm has to move, in disengaging one contact and engaging the other. contact, to increase the sensitivity of the switch, as for operation as a feeler switch.

For this purpose, it has been proposed toprovide, in addi- An object of the present invention is to provide an improved and simplified snap action electric switch} Another object of the invention is to provide an improved and simplified snap action electric switch including only a single means or member adjustable as a function of a switch-actuating member.

A further object of the invention is to provide such a snap action electric switch in which such single means comprises an intermediate lever extending substantially parallel to a tension spring having one end connectedat a fixed point of a switch housing and its opposite end connected to .a contact arm and biasing this contact arminto pivotal bearing engagement with direction of action of the extension or tension spring as a function of the actuating member. This other adjustable means deflects the second point of action of the extension spring in the sense of accelerating the overriding of the dead center position, transversely or obliquely to the'direction of action of the tension spring. The first point of action of the tension spring is, of course,on the contact arm;

The resulting deflection forces acting in opposite directions at opposite ends of the extension spring then effect a rapid change of the inclination of the spring, with respect to the con tact arm. Conversely, the spring force acts on the switching system at two adjustable means. Depending on thed'esign of the system, the torques produced at the adjustable means, which may be, for example, angle levers, may be codirectional or may be counterdirectional, and thus mayadd to or subtract from each other to attain automatic resetting of the switching system. Especially when the torques act counter to each other, appreciable advantages result because, for example with the use of a strong tension spring, which has an advantageous effect on the contact force, only relatively small actuating forces are necessary.

It is furthermore cluding a switching system constructed inthe manner of a toggle joint, to provide, on a fixed intern'lediate'lever, a tappet or abutment for the tension spring which connects a rigid contact arm with a fixed suspension point through the tappet. However, since in this known arrangement the intermediate lever is not mounted outside of any possible direction of action of the tension spring, thetappet is necessary, in this case, to make possible an automatic resetting of the switching system.

SUMMARY OF THE INVENTION ble with prior art constructions are attained. using only one means adjustable as a function of the actuating member.

known, in a snap action electric switch inthe intermediate lever.

Yet another object of the invention is to provide such a snap action switch in which the intermediate lever is pivoted in the housing intermediate its ends, withitsarm extending toward the fixed suspension point of the spring carryingabutment means engageable with the tension spring-at a point intermediate the ends of the latter and acting on the'spring in a direction substantially transversely of the line connecting the two suspension points of the spring.

Afurther objectof the invention is to provide such a snap actionswitch in which the abutment means acts on both sides of the spring during pivoting of the intermediate lever.

Still another object of the invention'is to provide such a snap action switch in which the abutment means embraces the contact spring. 1

- A further object of the invention is to provide such a snap action electric switch inwhich the abutment means acts on only one side of the spring.

. BRIEF DESCRIPTION OF THE DRAWINGS For an understanding of the principles of-the invention,

reference is made to the following descriptionof a typical em- DESCRIPTION or THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, a snapaction electric switch embodying the invention is illustrated as comprising a housing 1 having extending, through the walls thereof, electrically conductive leads 2-, 3 and 4 and serving to connect the The present invention utilizes the concept of adjusting the tension spring at two-spaced points of the switching system, with utilization of the reaction forces. To this end, an intermediate lever, serving-as a single adjustable means, is arranged substantially parallel to the unilaterally suspended tension spring having its ends fixed in a known. manner. The tension spring extends substantially, centrally of the longitudinal ex tent of the lever. The intermediate lever'carries, at its end or arm projecting toward the fixed suspensionpoint of the tension spring, abutment means or a tappet for the tension spring and acting on the latter at a point located between the spring suspension pointsand in a direction substantially transverse to the line connecting the two suspension'pointsof the spring.

switchinto a circuit to be controlled. The'ends of the leads 2 and 3 within housing I carry contact'rivets-fi and'7 which cooperate with a movable contact 8. Contact 8 is secured to a' rigid contact arm 9 near the free end of the latter, and the opposite end of contact arm 9 has pivotal bearing engagement in one arm of an L-shap'ed intermediate lever 10 of electrically conductive material. Lever 10, in turn, is pivotally mounted, intermediate its ends, on an electricallyconductive bearing or fulcrum 4 forming part of the lead 4. Contact arm 9 and inter- 10 which extends toward contact arm 9, member or button 14 transmitting mechanical forces to intermediate lever 10.

As best scenin FIG. 2, the bearing orbase end of contact arm 8 is forked, and the arm of lever loproviding a bearing forcontact arm 9 is also forked. Thereby, tension spring 11- connected-to contact arm 9 and to fixed point 13 can move freely. Spring 11 is deflected away from the straight line interconnecting its two suspension points by means of abutment means 12, which latter includes a lower abutment surface 12 underlying spring 11 and an upper abutment surface 12" extending substantially parallel to surface 12' and overlying spring 11.

With the arrangement thus described, if an inwardly directed force acts on actuating member or button 14, member 14 is displaced inwardly of housing 1 and, in turn, displaces or adjusts intermediate lever '10. Lever is thereby pivoted clockwise, as viewed in FIG. 1., with the bearing point thereon of contact arm 9 moving downwardly, also as viewed in H6. 1. At the same time, abutment means 12 moves upwardly so that its abutment surface 12' engages and lifts the intermediate portion of spring 11. Due to this bilateral action, the angle of inclination of tension spring 11 relative to contact arm 9 changes relatively rapidly in the sense of accelerating the overcoming of the dead center of contact arm 9. As soon as the dead center position is overcome, movable contact 8 snaps out of engagement with counter contact or rest contact 7, with which it is normally engaged, and snaps into engagement with reversing contact 6. In the rest position of contact 8 in engagement with contact 7, the switch interconnects leads 3 and 4. After the switching of contact arm 9, by actuation of actuating member or button 14, the switch establishes an electrical connection between leads 2 and 4 and, upon release of the force from actuating member or button 14, the switching system automatically returns to the rest position shown in FIG. 1.

Tension spring 11 acts on intermediate lever 10 at two different points. On the one hand, contact arm,9 bears against a bearing point of lever 10 and, one the other hand, a force transversely of the axis of spring 11 is transmitted to spring 11 through abutment means 12.

These two forces produce opposite. moments or torques on intermediate lever 10, with the magnitudes of the forces being so matched that there is a resulting counterclockwise moment effective on intermediate lever 11 in all possible positions of the latter. By selection of another fixed suspension point l5, 16 or 17, for anchoring the fixed end of spring 11, the actuating force necessary to be applied to actuating member or button 14 can be varied within wide limits without appreciable change in the contact pressure. If, for example, spring 11 has a fixed suspension point at the fixed point 15, only a small actuating force need be applied to actuating member or button 14. This is an important advantage of the present invention in that, in known arrangements, the required actuating force can be reduced only with the use of weaker springs and at the expense of the contact pressure. Anchoring of the fixed end of spring 11 to any fixed point other than point 15, such as at the fixed points 13, 16, or 17, results in an increase of the force required to actuate the switch. The resulting moment on intermediate lever 10 may be the result of either subtraction or addition of the two operative partial moments.

it will be understood by those skilled in the art that the particular abutment means 12 illustrated in the drawings may be replaced by an abutment engageable with only one side of spring 11, unless the construction is such that the force exerted on abutment means 12 changes direction within the free end movable between said stops; a, tension sprin having one end connected to a first suspension point on sat contact arm spaced from its bearing end, extending substantially parallel to said lever in substantially central alignment therewith and in laterally spaced relation to said fulcrum, and having its opposite end connected to a second and fixed suspension point on said housing beyondsaid fulcrum, said spring biasing said contact arm into bearing engagement with said lever to exert a torque tending to pivot said lever in one angular direction about said fulcrum; and abutment means on the second arm of said lever extending toward said fixed point, said abutment means embracing said spring to act on opposite sides of the latter at a point beyond said fulcrum and intermediate the ends of said spring to deflect said spring, from a straight line connecting said first and second suspension points, in a direction to increase the tension of said spring acting on said lever, through said abutments means, to exert' a torque tending to pivot said lever in the opposite angular direction about said fulcrum; said abutment means, upon pivoting of said lever by displacement of said actuating member, acting on said spring to deflect said spring in the opposite direction from the straight line connecting said first and second suspension points to snap said contact arm, by pivoting about its bearing end on said lever, from a rest position in which its free end engages one stop, to an actuated position, in which its free end engages the other stop, and to provide a restoring force acting to return said contact arm to its rest position; the line of action of said tension spring remaining in spaced relation to the same side of said fulcrum and out of engagement with said fulcrum in all positions of said switch.

2. Asnap action electric switch, as claimed in claim 1, in which the arm of said lever providing a bearing for said contact arm is substantially L-shaped, the contact arm bearing on that leg of the L-shape which extends substantially normal to the general longitudinal extent of said lever.

3. A snap action electric switch, as claimed in claim 2, in which that end of said contact arm bearing on said lever is forked, and the leg of the L-shaped arm of said lever, on which said contact arm has bearing engagement, is also forked; said spring extending between the arms of the two forks for free movement of said spring.

4. A snap action electric switch, as claimed in claim 1, in which each of saidstops is a respective electric contact connected to an external circuit, and a movable contact on the free end of said contact arm is engaged, in the-rest position of said contact arm, with one of said first-mentioned contacts; and an external lead electrically connected to said movable contact.

5. A snap action electric switch, as claimed in claim 1, including a plurality of fixed'suspension points for said spring in said housing; said'suspension points being arranged in a row 

